This is a variation of the often suggested hike Sonogno - Prato Sornico. Both hikes go from Verzasca to Maggia valley through Passo di Redorta. The hike ending in Prato Sornico is about an hour shorter but misses a fantastic pearl - the lake Tomeo.

Unlike most hikes in Verzasca Valley, this one doesn't really take you through the forest but the whole way up you can enjoy incredible views (if you don't have 8.5hrs for a hike, the first section to Puscen Negro takes just over an hour and is in itself a magnificent hike). You then climb up to Passo di Redorta where you can look down at both Verzasca and Pertus valleys. The views from up there are incredible. After about 30 min of decent you'll see a blue trail going off to the left towards Lago di Tomeo. Make sure you take this one, otherwise the red trail will take you to Prato. The blue section leads up to another pass, one that separates Pertus and Tome valleys. This part can be a bit dangerous -- when I did this hike in October this section never got any sun and the rocks were very slippery.

Once in Tome Valley you first decent towards the breathtaking lake Tomeo with Rifugio Tomeo right next to it where you can spend a night. The trail itself doesn't really give you good views of the lake so it's highly recommended that you take a few minutes to go from the hut down to the lake and enjoy the view. The best spot is at the other end of the lake--the walk there and back takes about 20min-25min. The rest of the hike is a decent towards Broglio where you can catch a bus to Locarno.